12v Camper Electrics

[nitro23456]

Hi all

Bought a cheap camper that has 6x 12v LED spots wired into the ceiling liner but the previous owner has wired them off the main car battery.

They are turned on by a wall switch in the back that has 3 terminals - live, switched and ground.

I have now added a leisure battery and various other circuits (USB charge points etc) off this leisure battery without problems. But am running into issues trying to transfer this existing light circuit over to the leisure battery mainly because i dont want to strip the whole lining out and can't fully see what has been done.

Basically, there are currently 2x two-core cables at the switch each containing a live and ground cable but only the reds are connected at the switch. Each has a black ground cable that goes off somewhere to presumably a grounding point somewhere on the chassis. I have run new live and ground cables to the existing switch from my new fusebox. I have identified which existing cable was the permanent live and swapped for my new live from the leisure battery and this time connected my new ground cable at the switch (previously no ground at the switch as the blacks go off somewhere behind the wall). I am then utilising the original switched live cable that goes to the lights but I can't see exactly where its black core goes.

However, when i energise the new circuit, the fuse pops.

Please see my diagrams below. Could it be because the old ground goes off somewhere unknown?

 

[davelx]

You should find that one of the incoming red/black pairs goes to the battery , i.e. is the feed. The other red black pair should go to the lamp.

Link the two blacks together with an insulated connector block. Only the reds need connect to the switch (only two terminals needed - C and either L1 or L2).

A normal three terminal light switch has L1,L2 and C(ommon) connections on the actual switch body. There may be as separate earth terminal at the side, which can be connected to the the black terminal block.

The way your diagram shows it, in one position the switch will be short-circuiting the feed, which is why the fuse pops (just as well, otherwise the cables could catch light).

 

[EFLImpudence]

This is what you should have if the leisure battery negative is not connected to ground - the body.

However, if the negative IS connected to ground then you just connect the lamp negative to ground anywhere.

You may have to reconnect the switch depending on what it does.
You only need a two terminal one.

 

[nitro23456]

Thanks both, thats really handy.

I think the mistake ive made is that when wiring my other circuits for USB charge points, I've used the little rocker style switches with an LED like the attached and these need the ground wire for the little LED to light up?

I've then followed this pattern to the light switch for the main lights but the switch is like the other attachments. God knows why it has 3 terminals then. None are labelled.

The leisure battery IS grounded. So to cut a long story short, i can take the new black cable i've already now run and connect it together with the black from the light cable. Then just have the new red from leisure battery and the light cable's red at the switch. Ive already disconnected the original 2 core from the starter battery.

 

[EFLImpudence]

I think the mistake ive made is that when wiring my other circuits for USB charge points, I've used the little rocker style switches with an LED like the attached and these need the ground wire for the little LED to light up?

Ah.

I've then followed this pattern to the light switch for the main lights but the switch is like the other attachments. God knows why it has 3 terminals then. None are labelled.

You will have to determine what the contacts do with a multimeter.
They could be off/on1/on2 or off/on1/on1&2 or on1/off/on2.
Were there no instructions with them, or on-line where you bought them?

The leisure battery IS grounded. So to cut a long story short, i can take the new black cable i've already now run and connect it together with the black from the light cable. Then just have the new red from leisure battery and the light cable's red at the switch. Ive already disconnected the original 2 core from the starter battery.

Yes, I think so.

 

[EFLImpudence]

From what I can find, they are described as two-way switches.

If they mean the same as we do then they will be on1/on2.

 

[SimonH2]

Some of these rocker switches do contain an indicator in them - but the switch itself is a change over.
Correct wiring would be (using the terminal numbers in the OP's diagram) :
Live feed to 3
Load to 2
Ground/chassis to 1
The internal indicator would be between 2 and 1, and shorted out when the load is off. But which terminal is 1, and which is 3, needs to be figured out - with a meter, or bulb & battery.

 

[EFLImpudence]

The OP's does not appear to have an indicator and is described as a two-way switch (change over) which would require the three terminals - so connecting one of the terminals to ground would not be advisable.

 

[SimonH2]

It actually works fine as long as the load is connected to common. Doing that with domestic lights would probably cure all the glowing/flashing lights problems people report !

 

[EFLImpudence]

What works fine? What am I missing?

Connecting the negative (neutral) to a two-way switch does not work fine.

 

[SimonH2]

Yes it does.
Using terminology we're used to, connect L to L1, N to L2, and load to COM. Unless the switch fails, no shorts - load is either connected to L or connected to N.This is EXACTLY how some of the switches with built in indicators are designed to be wired.

If wired like this, it would deal with the leakage issues that cause LED and some CF lamps to either glow or flash. When off, the switch live would be connected to N and dissipate any leakage current.

 

[EFLImpudence]

Yes - unless.

It's a camper van. Why would anyone want to run an unnecessary negative to a switch?
Even if the negative wire passes the switch, why would anyone want to unnecessarily cut it and unnecessarily connect both to the switch?

Apart from that, there appear to be no markings on the switch in question.

 

[SimonH2]

Well, it's common to use 2 core cable, and it's common to "loop at the switch", especially for lights where the supply comes from floor level and the load is at roof level - even more so when it's an add-on rather than something installed by the manufacturer using a factory made loom when it would make sense to minimise cable usage. So quite reasonable to have the negative (or chassis ground) present at the switch.
And yes, if you have an uncut cable it makes sense to not cut the negative. But if you have 2 cut ends, then you do need to join the negatives - and there's a handy spare terminal on which to park the joint, but you don't have to use it.

But the main argument for connecting the negatives as described (though not in this case) is that for the indicator to work in many of them, then you MUST connect it that way.

Switch doesn't need markings if you are familiar with them. I've used loads of these "simple" rocker (and toggle) switches of various styles over the years. Every one I can remember has had the same terminal arrangement - 3 terminals in a row, centre is common, the other two are the two switched terminals. And also, every one I can remember using has had the terminals in such a way that whichever way you operate the rocker or toggle, it is the opposite end terminal that connects to common - down to the way that the internal rocker contact operates. And some of the (cheap) illuminated ones I've used have simply added a bulb between centre contact and one end contact (some may have used a shorter contact so the switch plate doesn't touch it, some definitely didn't).
Double pole switches simply have two rows of terminals in a wider body.

CBA to do a diagram right now, so a description will have to do. Inside, there's a brass plate that is pivoted on the inner end of the centre terminal. When it rocks one way, it touches one outer terminal; when it rocks the other way, it touches the other end terminal.
The operating devices, whether rocker or toggle, is pivoted in the front of the switch case. On the rear of it (ie inside the switch) there is a spring loaded plunger sticking out which is pushing on the brass plate. Depending on which side of the pivot it pushes on, the rocker moves one way or the other.
So you can now see that when you put the rocker down, the other side of the pivot, the plunger moves up. When it gets past half way, the brass plate flicks over so it now touches the top terminal - and the geometry of the plate and plunger makes the rocker (or toggle) flick to the end of it's travel with a click. A truly on/off switch can simply omit one of the end terminals.
If you were wondering, yes I've had a few apart to see if I could repair them - some I have repaired, others I just took apart out of curiosity.
With this example from Halfords you can see (in the third picture) how they've just stuck a label on to show the terminal functions. Contrast with the non-illuminated version, you can see that they just omitted the third terminal and used the same case mouldings. If you look at the three position version (just needs a different pivot arrangement to provide a centre-off), the marking show how the "connected" pole is opposite to the direction the toggle is placed.
If you look at most of the switches in their range, you'll see the same basic arrangement on the majority of them.

 

[SUNRAY]

Yes it does.
Using terminology we're used to, connect L to L1, N to L2, and load to COM. Unless the switch fails, no shorts - load is either connected to L or connected to N.This is EXACTLY how some of the switches with built in indicators are designed to be wired.

I have found a number of domestic 2 way switched systems wired this way, including some with an intermediate switch.

If wired like this, it would deal with the leakage issues that cause LED and some CF lamps to either glow or flash. When off, the switch live would be connected to N and dissipate any leakage current.

In my home I used an intermediate switch at one end of a 2 way circuit with a resister to neutral to stop LED's glowing permanently.

 

[SimonH2]

I have found a number of domestic 2 way switched systems wired this way, including some with an intermediate switch.

Would that be the method where both ends of a switched off light can be live ?